Heretofore prior art packaging schemes for utilizing substrate means bearing planar circuit means and operating in the microwave frequencies has been to install such substrates into a reversible protrusion box or cavity of a milled out material using a paste down method such as conductive glue, epoxy sheet or indium solder. These methods work, but it is very difficult or in some instances impossible to repair or replace the substrates.
Other prior art utilizes press down retainers, some of which include an embossed or quilted foil on the metalized side of the substrate, to install the substrates into a box or cavity. The press-down method is satisfactory where small substrates are employed, but are unsatisfactory when large substrates are used and will, environmentally speaking, deteriorate in time.